Mixed core design for power transformers to reduce core losses

Abstract

The European Parliament has recently passed eco-design requirements with regards to small, medium and large power transformers. As core losses limit the efficiency of power transformers, it is of great importance to be able to calculate these losses during design stage and to reduce those by improvements in core design. Nowadays transformer cores are made of one electrical steel sheet grade. Its magnetic properties determine the no-load power loss of the transformer. This paper presents a combination of finite element simulation and post-processing algorithm to calculate transformer core losses. Based on this loss simulation concept, mixed cores consisting of two different electrical steel qualities are investigated. At first, a real power transformer is used to verify this concept by comparing measured and simulated losses. In the second part of this work, the selection of appropriate steel quality combinations is explained and applied to the modeled power transformer. Finally, economic aspects evaluate the loss reduction of a mixed transformer core design.